Like I said upthread, Mara, I’m afraid the fact that your bandits never met Breden is one reason they might be more susceptible to xhis charm if they do meet xhim while Lady Mara is still off in the Xaos-lands:
By contrast, a band that had Breden around, got poisoned, and had xhim escape from custody will have a lot more actual reason to be hostile.
The idea that Lady Mara might have tried to make Breden the Judas of her religious cult – remembering, again, that in-game Mara has about 500 worries more pressing that the slim chance of Breden reappearing – feels to me like out-of-game knowledge affecting your role-play. A leader who spends too much time ranting about a helot that the band has never met and probably never will as “Judas Demon” would in any case be vulnerable to people deciding that was a little bit over-the-top. Especially as and when said helot shows up as the leader of another successful rebel band and suggests something reasonable, like closer coordination between their attacks.
So I disagree that there’s a plot hole, or that Breden’s charisma would have to be godlike to influence your band. But don’t panic, and certainly don’t give up. Xhe won’t be able to outright steal your band–not this game, and not in future games if you keep using your charisma to drive a wedge between xhis followers and yours. (Or, you know, have xhim killed.)
I think we’re talking human cannonball speeds rather than jet speeds–say, up to around 100 mph. So messages can take a while to get to the Halassurq front. @Norilinde, Telos-sense will keep a flying Theurge from running into a mountain even in poor visibility conditions and makes it easy to e.g. follow a coast, but in terms of not getting lost while flying inland they usually have to navigate visually, with a map and compass to hand to keep them from getting disoriented in unfamiliar terrain. Flying in bad weather or at night is possible but runs a higher chance of realizing when the sun comes up that you’re hopelessly lost. They don’t use special landmark towers; towns and villages make good enough landmarks for such purposes.
You’d think…but mature heliography appears to be a 19th century tech in our world, despite the fact that Hooke had the idea for some similar signal tower system in the 17th century…so I’m happy not including it in the gameworld.
You misconceive them entirely. 
Your MC has more vanity than the Diadoch, who’s much too pragmatic.
There will be some limited scope for that, yes. But not to invent heliographs, rifles, hot air balloons, transfusion, steam-engines AND all the other stuff discussed on the various XoR threads. One or two techs, not the raft of them.
They get out of breath more easily and have a moderately higher rate of cardiac problems.
It is feasible in theory, yes. (And you rightly interpret the mullow comment.) So, good suggestion, and let’s add anaesthetic to the list of techs that a high-INT rebel might be able to develop in later games.